1. Field of the Invention
This invention relates generally to sewing machines, and more particularly to material/fabric tensioning devices for those sewing machines.
2. Prior Art
The advent of computer controlled devices obviated the need for full manual operation of many crafts. One in particular is the stitching and embroidery art. The material being sewn is no longer guided in a convoluted path under the needle by hand, but is done so automatically, after being secured to a frame arrangement movable on the sewing machine base. The frame arrangement is movable in the horizontal X and Y directions due to engagement with computer controlled stepping motors, a frame arrangement being shown in U.S. Pat. No. 3,988,993, and assigned to USM.
This arrangement works well when the material being stitched is something heavy or thick, such as the denim patch-type pocket material of dungarees, or the like. Pattern stitching does not work well however, when the material is thin and flimsy, in which the material is pulled askew when the lower thread beneath the material is tensioned and pulls on the material, which yields or wrinkles, thus distorting the material and damaging the workpiece.
Thus, it is an object of the present invention, to eliminate the problems encountered when automatically stitching a pattern into fine or thin cloth like material.
It is a further object of this invention to be able to tension any web of material in a frame, which material is being stitched by a sewing machine.
It is yet a still further object of this invention, to provide a tension mechanism which can be regulated to tension a material a particular distance and then stop, and which allows the material to be tensioned with a high force that prevents any movement or shifting of the material by the action of the needle and also prevents overstretching of the material which would otherwise distort the final stitch pattern.